Gas-filled ignitron



Oct. 10, 1939. J s m 2,175,924

GAS-FILLED IGNITRON Filed June 19, 1937 Load WITNESSES; INVENTOR @w/ Joseph 5/e 0/a/7 M 'BY ATTOR'NEY Patented Oct. 10, 1939 UNITED STATES PATENT OFFICE GAS-FILLED IGNITRON Vania Application June 19, 1937, Serial No. 149,248

6 Claims.

My invention relates to electric discharge apparatus, and has particular relation to discharge apparatus in which discharge devices having ignition electrodes are incorporated.

By a discharge device of the type having an ignition electrode I mean a device comprising a cathode of mercury or other suitable metal, an anode disposed so that a discharge may pass between it and the cathode and an ignition electrode disposed adjacent to or in contact with the cathode. When a current is transmitted between the ignition electrode and the cathode a discharge is initiated between the anode and the cathode.

In. the following discussion and in the claims I shall refer to an electrode of the mercury pool type. This expression shall be defined for the purpose of the present application as including in addition to an electrode of liquid mercury electrodes of other metals such as lead, cadmium, caesium, etc., which function similarly to a mercury pool electrode.

In the following discussion and in the claims I shall also refer to an ignition electrode. For the purpose of the present application, the latter expression shall be taken to define generally an electrode disposed adjacent to or in contact with an electrode of the mercury pool type which cooperates with the electrode of the mercury pool type to produce a discharge between the latter and another cooperative electrode. In general, the ignition electrode may be displaced from the electrode of the mercury pool type. However, in the preferred practice of my invention the ignition electrode is in contact with the mercury pool electrode and is composed of a bar of high resistant material, such as silicon carbide, boron carbide or boron. When in the following discussion and in the claims I refer to an electrode of the silicon carbide type I mean thereby any high resistance ignition electrode which may be composed not only of silicon carbide but of any other suitable material such as boron carbide or boron.

When the ignition electrode of a discharge device is a bar of the silicon carbide type, I have found that a discharge may be initiated between the anode and the cathode by transmitting current between the ignition electrode and the cathode at any moment when the anode is at a moderate potential positive relative to the cathode.

The anode and the cathode of a discharge device of the type having an ignition electrode operate in a gas-tight container and in accordance with the teaching of the prior art of which I am aware, the container is also highly evacuated.

The container is in general provided with metallic walls separated by insulators sealed to the metallic walls. The provision of a container of this type which is completely air-tight and does not leak has proved to be difficult in the past. 5 In general, a container has been considered satisfactory in which the leakage is relatively slow so that after a period of the order of a year the operation has become impaired to such an extent as to render the discharge device useless. This 10 situation not only results in considerable expense but gives rise to considerable inconvenience to the user of the discharge apparatus.

It is accordingly an object of my invention to provide a discharge device of the type having an 15 ignition electrode which shall have a long life compared to that of the prior art devices.

Another object of my invention is to provide a discharge device of the ignition electrode type in which the anode and cathode are disposed in an air-tight container of such character that the leakage shall not seriously impair the operation after a relatively short time of the order of a year.

More specifically stated, it is an object of my invention to provide a discharge device of the g5 ignition type particularly adapted to low potential operation that shall have a long life in spite of the fact that the container is subjected to the usual slow leakage.

My invention arises from the realization that 30 when the apparatus is operated at relatively low potentials the back potential is also comparatively low and the tendency to backfire is correspondingly reduced. I have realized, moreover, that the tendency towards backfire depends directly on the 35 pressure of the gas present in the discharge device and increases as the pressure of the gas increases. Accordingly, if the back potential is reduced the pressure of the gas present in the container may be increased. Hence, a discharge 40 device that is to operate at relatively low potentials may contain gas at a considerable pressure. The presence of gas, at a sufiicient pressure, moreover, would prevent the leakage of air into the air-tight container. 45

In accordance with my invention, therefore, I provide a discharge device in which an inert gas, and preferably a noble gas such as argon and neon, is present in the container at a pressure i of several atmospheres. The leakage of this gas 50 outward is relatively slow and the life of the container is considerably increased.

The novel features that I consider characteristic of my invention are set forth with particularity in the appended claims. My invention itself, however, both as to its organization and its method of operation, together with additional objects and advantages thereof, will best be understood from the following description of a specific embodiment when read in connection with the accompanying drawing, in which the single figure is a diagrammatic view showing a preferred embodiment of my invention.

The apparatus shown in the drawing comprises a discharge device having an insulating cylindrical wall 3 composed of a material such as glass or porcelain, for example, and metallic bases 5 and l. The bases 5 and l are sealed to the insulating wall 3 and a pool 9 of mercury is disposed in the bottom of the container thus formed and rests on the lower base 5. The upper base 1 is provided with a circular opening into which an insulating plug ll carrying an ignition electrode l3 of the silicon carbide type is sealed. When the plug H is in place the silicon carbide type electrode l3 dips into the mercury pool 9. The upper base I of the container may, moreover, cooperate as an anode with the mercury pool cathode. Before being sealed off the container thus formed by the insulating wall 3 and metallic bases 5 and l is highly evacuated and filled with an inert gas such as neon or argon, or any combination of such gases at a pressure of several atmospheres.

In the practice of my invention the discharge device may be utilized for many purposes. Its most common use is as a rectifier. In such a case an alternating potential is impressed from a suitable supply transformer i5 between the mercury pool cathode!) and the upper base 1 which operates as anode through the load l'! supplied. The ignition electrode 1 3 is connected to the secondary 19 of the transformer through a rectifier 2| of suitable type and through the cathode 9 of the discharge device.

The potential of the source and the load properties are such that the back potential impressed on the discharge device I is not of sufficient magnitude to produce backfire in the presence of the gaseous atmosphere.

While my invention has been illustrated herein as applied to a discharge device of a specific structure, it should in no way be regarded limited to this structure. For example, the discharge device may be of symmetric rather than asymmetric structure. In such a case the container is com monly U-shaped and is provided with two principal electrodes both of the mercury pool type. In lieu of having a single anode or a single cathode, the discharge device may also be provided with a plurality of anodes or a plurality of cathodes.

' Although I have shown and described a certain specific embodiment of my invention, I am fully aware that many modifications thereof are possible. My invention, therefore, is not to be restricted except insofar as is necessitated by the prior art and by the spirit of the appended claims.

I claim as my invention 1. A discharge device comprising at least a single electrode of the mercury pool type, at least another electrode, said electrode of the mercury pool type and said other electrode being disposed in a substantially gas-tight container of such structure that slow leakage of gas through the walls thereof is possible, an ignition electrode for initiating a discharge between said mercury pool type electrode and said other electrode and an inert gas at a pressure substantially greater than atmospheric pressure for directing said leakage in a direction out of said container.

2. A discharge device comprising at least a single electrode of the mercury pool type, at least another electrode, said electrode of the mercury pool type and said other electrode being disposed in. a substantially gas-tight container of such structure that slow leakage of gas through the walls thereof is possible, an ignition electrode for initiating a discharge between said mercury pool type electrode and said other electrode and a noble gas at a pressure substantially greater than atmospheric pressure for directing said leakage in a direction out of said container.

3. A discharge device comprising at least a single electrode of the mercury pool type, at least another electrode, said electrode of the mercury pool type and said other electrode being disposed in a substantialy gas-tight container of such structure that slow leakage of gas through the walls thereof is possible, an ignition electrode for initiating a discharge between said mercury pool type electrode and said other electrode and an inert gas at a pressure of the order of several atmospheres for directing said leakage in a direction out of said container.

4. A discharge device comprising at least a single electrode of the mercury pool type, at least another electrode, said electrode of the mercury pool type and said other electrode being disposed in a substantially gas-tight container having metallic walls and of such structure that slow leakage of gas through the walls thereof is possible, an ignition electrode for initiating a discharge between said mercury pool type electrode and said other electrode and an inert gas at a pressure substantially greater than atmospheric pressure for directing said leakage in a direction out of said container.

5. In combination, a discharge device comprising at least a single electrode of the mercury pool type, at least another electrode, said electrode of the mercury pool type and said other electrode being disposedin a substantially gas-tight container of such structure that slow leakage of gas through the walls thereof is possible, an ignition electrode for initiating a discharge between said mercury pool type electrode and said other electrode and an inert gas at a pressure substantially greater than atmospheric pressure for directing said leakage in a direction out of said container, and means for impressing a potential between said mercury pool type electrode and said other electrode, the forward component of which is of sufiicient magnitude to produce a discharge between the said electrodes when the ignition electrode is excited and the back component of which is insufficient to produce a backfire discharge in the presence of said gas.

6. A discharge device comprising at least a single electrode of the mercury pool type, at least another electrode, said electrode of the mercury pool type and said other electrode being disposed in a substantially gas-tight container of such structure that slow leakage of gas through the walls thereof is possible, an ignition electrode for initiating a discharge between said mercury pool type electrode and said other electrode, said ignition electrode consisting of a bar of the silicon carbide type in contact with the electrode of the mercury pool type, and an inert gas at a pressure substantially greater than atmospheric pressure for directing said leakage in a direction out of said container.

JOSEPH SLEPIAN. 

